A dozen natural-gas drilling companies possibly violated federal law by injecting more than 32 million gal of diesel fuel and diesel-laced fluids into the ground between 2005 and 2009 without first obtaining permits from EPA, Democrats from the House of Representatives said last week. “The industry has been saying they stopped injecting toxic diesel fuel into wells,” said Rep. Henry A. Waxman of California, the ranking Democrat on the House Energy & Commerce Committee. “But our investigation showed this practice has been continuing in secret and in apparent violation of the Safe Drinking Water Act.” The diesel fuel was used by the companies in a controversial practice known as hydraulic fracturing, which involves the high-pressure injection of water, sand, and chemical additives into shale rock formations deep underground. In a letter to EPA Administrator Lisa P. Jackson, Waxman and two other Democratic members of the energy committee said the companies had no information on whether diesel fuel had contaminated drinking water supplies near the drilling sites. Industry officials have long maintained that hydraulic fracturing operations are safe. “EPA has no instances where diesel fuel ever migrated into drinking water,” argues Lee O. Fuller, vice president of government relations at the Independent Petroleum Association of America.